Method of manufacturing propellers



Dec. 20, 1932. H. F. SCHMIDT I METHOD OF MANUFACTURING PROPELLERS Filed Jan. 11, 1930 2 Sheets-Sheet l I INVENTOR 1 16.4- HENQY E'ScHMIDT. BY

ATTORNEY Deg. 20, 1932.

H. F. SCHMIDT METHOD OF MANUFACTURING PROPELLERS Filed Jan. 11. 1930 2 Sheets-Sheet 2 v HENQY if SCHMIDT.

R. ATTORNEY Patented Dec. 20, 1932 UNITED STATES PATENT OFFICE HENRY F. SCHMIDT, F LANSDOWNE, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSE .ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA METHOD OF MANUFACTURING PROPELLERS Application filed January 11, 1930. Serial No. 420,212.

My invention relates to a method of manufacturing propellers and it has for an object to provide a method of the character des ignated which shall be less expensive, more rapid and more accurate than the methods heretofore employed.

These and other objects are effected by my invention, as will be apparent from the following description and claims, taken in connection with the accompanying drawings,

forming a part of this application,-in which:

Fig. 1 is a plan view of one form of propeller which may be constructed in accordance with my method;

Fig. 2 is a developed view of the peripheral or tip edge of the blades of the propeller shown in Fig. 1 and of a cross-section through the same propeller blades near their relatively thicker root portions;

Fig. 3 is'a cross-section of a propeller blade taken normal to the face of the blade and showing the attachment means between the propeller hub and the blade;

Fig. 4 is a plan view, drawn to a reduced 2 scale, of'a blank from which the propeller blades are formed; 1

Fi 5 is a radial section taken on the line V% of Fig. 4;

Fig. 6 is a section of a propeller blade hav- 30 ing a serrated root portion for attaching it to the hub;

Fig. 7 is a section of a propeller blade having a different form of root portion for attaching it to the hub;

Fig. 8 is an end view of the propeller hub having an incompleted propeller blade superposed thereon;

Fig. 9 is a partial section through a forging die and showing a blade therein; 40 ig. 10 is a cross-section through a proeller blade having variable thickness from 1ts leading to its trailing edges;

Fig. 11 is a view, in elevation, of a machine for turning propeller blank discs; and,

Fig. 12 is a plan view of the table of the machine shownin Fig. 11 with a propeller blank disc assembled thereon.

Assuming that it is desired to manufac ture a propeller such as shown in Figs. 1 to 50 3, a brief description of the form of such' a propeller will first begiven. This propeller comprises a hub 10 having a plurality of propeller blades 11 secured thereto. The type of propeller shown is intended primaril for 12 and 13 which diverge outwardly, each blade, as shown in Fig. 2, having an increasing axial pitch from the leading edge 12 to the trailing edge 13. The radial pitch of the blades is preferably constant. As shown particularly in Figs. 2 and 3, the blades, as disclosed and claimed in my copending application, Serial N 0. 420,213, filed January 11, 1930, entitled Propeller, and assigned to the Westinghouse Electric and Manufacturing Company, have a uniform thickness from their leadlng edges 12 to their trailing edges 13 and they have a gradually decreasing thickness from their root portions 14 to their tip portions 15, the working faces 30 of the blades being inclined or curved as shown in order to materially .reduce the centrifugal stresses set up in the root portions of the blades when the propeller'is operated at a relatively high speed.

In accordance with my improved method, the blades of the propeller are manufactured separately from the hub and c then attached thereto. Referring now to Fi 4, there is shown a flat blank 16 in the s ape of an annular disc from which the propeller blades are formed. The blank 16 is machined so as to have a radial cross-section such as shown in Fig. 5, which cross-section it will be noted corresponds to the section of the propeller blade shown in Fig.3. In this way, the blade is given the proper curved taper from its root 14 to its tip portion 15. Such a disc may be turned to the desired dimension and accurately and uniformly tapered at relatively small expense. The blades may, if desired, even be highly olished while they are in the disc form. gvhile I prefer to form the blank or disc 16 by a machining operation, it will be obvious that it also may be formed by forging, rolling, stamping, or other well known equivalent processes.

The blades of my propeller preferably have their root portions arranged somewhat like helices about the hub. By developing one of these blades into a single plane, it will be found that its root portion becomes substantially the arc of a circle having approximately twice the diameter of the propeller hub. Hence, I so form the blank or disc 16 that it has an inner diameter approximately equal to twice the diameter of the retaining groove in the propeller hub while its radial width is approximately equal to the length of a propeller blade from its root to its tip.

Hence, by providing a fiat blank or disc 16 (Fig. 4) having substantially the same cross-section as the blades (Fig. 3), and hav ing an inner diameter 16 approximately twlce that of the groove '17- in the hub (Fig. 3), I may provide a plurality of blades, for example, four, by merely cutting up the disc. I, therefore, show, in Fig. 4, four blades 18, 19, 20 and 21, respectively, laid out around the disc 16. After these blades are cut from the disc 16, they may be bent or warped so as to give them the proper form and the proper pitch (Fig. 2), after which they may be secured in the groove 17 of thehub in any approved manner as by weldlng at 22 and 23.

From the foregoing, it will be apparent that I have devised a method of manufacturing propellers wherein the propeller blades may be easily, rapidly and inexpenslvely manufactured. It will be noted that the entire machining operation is performed while the blade is part of a flat disc and that a single machining operation provides four blades. In this way, all the machining operations may be completed before the blades are warped into their final form. This is of considerable importance, particularly from a manufacturing view point, because if the blades are machined after they are cast or forged, and heretofore this has been cons1d ered as being absolutely necessary, the machining operations, due to the irregular shape of the blades, become long and laborious and very expensive. My improved method of making and assembling the blades therefore considerably simplifies and shortensthe process of manufacture and it also provides for reducing the cost of manufacture of propellers of the type described.

While, in Fig. 3, I show a means of attaching theb lades to a groove in the propellerhub by Welding, at 22 and 23, it will be obvious that other forms of attaching means may be employed such as, for example, interlocking projections or serrations on the root portion of each blade. Referring now to Fig. 6, I show a blade 24 having a root portion 25 provided with serrations 26 which diverge toward the tip of the blade, while, in Fig. 7, I show a blade 27 wherein the side walls 28 of the root 29 diverge outwardly toward the base thereof. In each of these figures, it will be noted that the outwardly-projecting portions of the blade root are intended to interfit with complementary recesses provided in the side walls of the retaining groove of the propeller hub. The blades shown in Fig. 6 and 7 are assembled upon their hubs by inserting or sliding their root portions into the grooves, the grooves having open ends in the transverse faces of the hubs.

When the propeller blades are attached to the hub by either of the methods shown in Figs. 6 and 7, that is, by sliding the blade into a groove in the hub, the root of the blade must be a true helix while the helical groove -in the hub must have uniform pitch. The

root of the blade, having been turned to a true circle because of being cut from a circular disc by the method heretofore referred to, will, ordinarily, not coincide exactly with the true helical groove in the hub and, while the difference in curvature is so small that it is not so important with blade fastening means of the welded type shown in Fig. 3, this difference in curvature is important, however, when the blade roots are serrated or otherwise provided with lateral projections which are slid or inserted into complementary projections in the retaining groove.

Referring now to Fig. 8, I show a cylindrical hub at 31 upon which is superimposed, in dot and dash lines, a propeller blade of the character shown in Fig. 7. It will be noted that the curvature of the base of the blade and the curvature of the bottom of the groove in the propeller hub are different. The maximum difference between these curves, or the maximum relative displacement of one curve with respect to the other is indicated by the reference character a. The point, therefore, that applicant wishes to emphasize is, that, in the construction of some types of propellers in accordance with the herein described method, there is a definite required relation between a and the depth or radial dimension of the serrations or root of the blade as indicated by the ref erence character 6 in Figs. 6 and 7, the requirement being that a be less than 7). As, long as this required relation is-maintained, it is immaterial whether the radius of curvature of the retaining groove be greater or less than the radius of curvature of the blade root..

Referring now to Fig. 9, I show a die 32 for changing the radius of curvature of the blade root so as to conform with the groove in the hub. From this figure, it w ll be clear that inasmuch as the dimension a is less than the dimension 6", the die 32 may obtain a proper grip upon the side walls 28 of the root 29 to force the root portion of the blade the distance a or to the point 33 of thedie so that the curvature of the blade root will coincide exactly with the groove in the propeller hub. It will also be apparent, from Fig. 9, that, if the distance a were greater than 6, it would be impossible to get the die 32 to grip the root portion at some intermediate portion, such as the portion 34. Of more importance, however, is the fact that if this condition is not maintained, the grooves or serrations in the die 32 will cross the grooves in the blade root and under such a condition it would be impossible to get the die to make a proper bite on the root portion and hence it would be impossible to warp the blade root to the proper form.

The propellers heretofore described have been provided with'blades which, although decreasing in thickness from their root to their tip portions, have had a uniform thickness from their leading to their trailing edges.

However, my method of manufacture is also applicable to propellers wherein the thickness of the blade changes from the leading to the trailing edge. For example, I showin Fig. 10 a cross-section of a propeller blade 36 which is, what may be termed, of aerofoil section. As will be apparent, the blade 36 has a relatively thick leading edge 37 and a relatively thin trailing edge 38.

In order to form blades of the character shown in Fig. 10 in accordance with my method, or in order to produce propeller blades having any degree of variable thickness from their leading to their trailing edges, the disc shown in Fig. 4 may be mounted upon suitable turning apparatus, for example, upon a table 40 of a boring mill indicated generally at 41 inFigs. 11 and 12. A suitable tool 42 is arranged in a manner well understood in the art to be free to move in a direction perpendicular to the table, and, in order to effect such movement in the proper timed relation to produce the correct thickness of the blades, a continuous cam 43 is arranged around'the table and a roller, such as the roller 44, is arranged to ride upon this cam and, in following the shape of the cam, to cause the tool 42 torise and fall and thus produce the proper depth of cut on the blank 45.

As will be apparent. the cam 43 has its profile so arranged that the disc may afterwards be cut into four sections or blades, each blade having a relatively thick leading edge as produced by the portions 47 of the cam and a relatively thin trailing edge as produced by the portions 48 of the cam. In the arrangement shown, the tool 42 'is held stationary while the table of the boring mill is adapted to rotate but it will be obvious that the table may remain stationary and the tool may be rotated, the only essential of such apparatus being that relative movement be produced between the cutting tool and the disc. The shape of the cam may be varied to provide blades having various contours from their leading to their trailing edges without departing from the spirit of my invention.

As stated heretofore, after the disc is machined, it is cut into segments 51, 52, 53 and 54, which segments are later warped or bent so as to give them the required shape before their assembly upon the propeller hub.

From the foregoing, it will be apparent that I have devised a method of manufacturing propellers, which method is less expensive, more rapid and more accurate than the methods heretofore employed. This is mainly accounted for by the fact that the blades of the propeller are completely formed or machined while they are part of a flat blank or circular disc of plate material and by the fact that a number of blades can be formed or machined simultaneously. It will be noted that my process is susceptible of not only manufacturing propeller bladesof uniform thickness, but also blades having a variable thickness from root to tip, as well as a variable thickness from their leading to their trailing edges.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is 1. The method of manufacturing a propeller blade having a variable thickness which includes forming a circular disc having the final variable thickness of the blade, dividing the disc, circumferentially, into a plurality of sections and thereafter warping the respective sections so as to form separate individual blades.

2. The method of manufacturing propeller blades which includes forming a circular disc having an inner diameter substantially equal to the diameter of a circle of which the base of a developed blade forms an arc, finishing the disc to a cross-section of a blade, cutting the disc into quadrants and bending the quadrants to form blades.

*3. The method of manufacturing a propeller blade having a variable thickness which includes forming an annular disc having an inner diameter approximately equal to twice the diameter of the propeller hub and a radial width approximately equal to the height of a blade from its root to its tip, machining the disc so that its radial cross-section is that of a blade of variable thickness, dividing the disc, circumferentially, into a plurality of sections, and bending the respective sections to form blades.

4:. The method of manufacturing a propeller blade having a relatively thick root portion and a relatively thin tip portion and a variable thickness from its root to its tip portion which consists in providing an annular blank with an inner, relatively thick root portion and a blade portion radiating outwardly from the root portion and diminishing in thickness toward the outer edge of the blank, cutting the blank, circumferentially, into sections, and warping the respective sections to form blades.

5. The method of manufacturing a propeller blade which includes forming a flat metal blank having the final thickness of the blade from its rootportion to its tip portion and from its leading edge to its trailing edge and in thereafter bending the blank so that its root portion is atrue helix and the remainder of the blades has an increasing axial pitch from its leading to its trailing edges.

6. The method of manufacturing a propeller which includes forming a cylindrical hub and providing helical grooves'of uniform pitch in the hub, forming an annular blank having a radial cross section which corresponds to the cross section of a propeller blade, the inner periphery of the blank comprising the blade root portion, cutting the blank, circumferentially, into a plurality of sections, warping the sections to form blades having root portions which are a true helix, and assembling the blades upon the propeller hub and securing their root portions in the respective grooves.

7. The method of manufacturing a propeller which includes forming a cylindrical hub having helical grooves of uniform pitch provided therein, forming an annular, fiat disc having an inner diameter approximately equal to twice the diameter of the hub and a radial width approximately equal to the height of a blade from its tip to its root, machining the disc so that its radial cross sec tion is that of a blade, dividing the disc, cir 'cumferentially, into a plurality of sections, warping the respective sections to form blades having the required pitch and having blade root portions which are a true helm, and assembling the propeller blades upon the hub and securing their root portions in the grooves thereof.

8. The method of making a propeller of the type described which includes machining a blade blank so that the base thereof is cut to the arc of a circle having approximately twice the diameter of the hub on which the blade is to be mounted, forming a helical retaining groove in the hub, forming complementary projections on the base portionof the blank and on the walls of the retaining groove, making the maximum radial depth of the projections greater than the maximum relative displacement of the developed helical trace of the retainin groove and the arc to which the base of the blade is formed, and warping the blade so that the projections on its base portion are a true helix and the re mainder of the blade has the required pitch.

9. The method of manufacturing propeller blades having a variable thickness from their leading to their trailing edges which includes forming an annular disc having an inner diameter which is approximately equal to the diameter of a circle of which the base of a developed blade forms an arc and having a radial width approximately equal to the height of a blade from its root to its tip portion, in machining the disc so that, circumferentially, it has a cross section composed of a plurality of leading-to-trailing-edge blade cross sections disposed in end-to-end relation, cutting the disc, circumferentially, so that each segment embodies one blade cross section and thereafter warping the respective sections to form blades.

10. The method of manufacturing a sectorshaped propeller blade from an arcuate blank which includes modifying the thickness of the blank suitably for a blade and warping the blank so as to provide a blade having'its axial pitch increasing from the leading to the trailing edge.

11. The method of manufacturing a sectorshaped propeller blade from an arcuate blank which includes modifying the thickness of the blank suitably for a blade and warping the blank to provide a blade having radial pitch which is substantially constant from the root to the tip and having axial pitch which irlcreases from the leading to the trailing e ge.

12. The method of manufacturing a pro, peller blade having a variable thickness which includes forming an arcuate blank having the final variable thickness of the blade, dividing the blank circumferentially into a plurality of sections and thereafter warping the respective sections so as to formseparate, individual blades.

In testimony whereof, I have hereunto subscribed my name this 9th day of January,

HENRY F. SCHMIDT. 

